I got curious about this set I found on the curb last year so I opened it up. Sound is OK but HV is out. I opened up the HV cage and there's not much there. Just a capped tube and the flyback HVT.

I noticed a weird thing that looks like it might be some sort of fuse or other protection device. I think its a resistor but its like nothing I've ever seen. Notice the burn mark on the top middle.

Any ideas?

HV cage in upper right corner (with hood up)
Socket for fusistor in lower right below & to the right of the black circular paper cap.

Originally posted by gonzothegreat
I got curious about this set I found on the curb last year so I opened it up. Sound is OK but HV is out. I opened up the HV cage and there's not much there. Just a capped tube and the flyback HVT.

I noticed a weird thing that looks like it might be some sort of fuse or other protection device. I think its a resistor but its like nothing I've ever seen. Notice the burn mark on the top middle.

Any ideas?


That component is a fusible resistor. These are wirewound and were often used in old radios/TVs as filament and/or B+ dropping resistors. They worked on the same princple as fuses--if there was a short in the filament circuit or B+, the fusible resistor would blow and open the circuit immediately, as would a fuse in the same position. The burned spot on yours indicates the part is defective.

Hope this helps.

Originally posted by Jeffhs
That component is a fusible resistor. These are wirewound and were often used in old radios/TVs as filament and/or B+ dropping resistors. They worked on the same princple as fuses--if there was a short in the filament circuit or B+, the fusible resistor would blow and open the circuit immediately, as would a fuse in the same position. The burned spot on yours indicates the part is defective.


Well, the filaments in the rest of the set light up so unless there are two filament circuits, that's OK. That leaves the B+ circuit. I'll take a look at what tubes it uses. I know I have a tube tester around here. There is also an old black paper covered cap that might be suspect.

Thanks for the component ID! Now where can I get a replacement or two since I'll probably blow one or two before it gets better?

Originally posted by gonzothegreat
Well, the filaments in the rest of the set light up so unless there are two filament circuits, that's OK. That leaves the B+ circuit. I'll take a look at what tubes it uses. I know I have a tube tester around here. There is also an old black paper covered cap that might be suspect.

Thanks for the component ID! Now where can I get a replacement or two since I'll probably blow one or two before it gets better?


You might try Radio Shack--they might have a few fusible resistors left in their inventory (although they are very scarce these days, as today's TVs don't use them). Failing that, I'd ask around at TV repair shops that have been in business awhile (long enough to have serviced tube-type TVs); they may have a few of these beasts lying around.

Since I responded to your post, I've been thinking about the HV problem in your RCA New Vista TV and have come up with some suggestions. You mentioned a "capped" tube in the HV cage near the flyback. In a black-and-white set this is the HV rectifier (and the only tube, period, in the cage); the cap is the plate connection, IIRC. If this is a color set, you will have two tubes in the HV cage with caps on them; one is the HV rectifier, as before, while the other will be the HV regulator (6BK4; the HV rectifier is usually a 3A3, though a couple other types were used by different manufacturers). If you have no HV, one or both of these tubes may be defective (or dead altogether); a dead HV rectifier always kills the raster, as will defective horizontal oscillator, output or damper tubes or defective components in these circuits. If the flyback is running excessively warm, or so hot the wax is melting, it might be defective (shorted).

Keep in mind that if the horizontal oscillator is far off frequency, it can kill the raster as well. However, be careful: In tube-type TVs with power transformers, it is possible to burn out the transformer if the horizontal oscillator is running too slow or not at all. The reason is that the horizontal output stage's plate current is regulated by grid-leak bias, obtained from the horizontal oscillator circuit. If there is no bias on the control grid, the current rises to the point where it overloads the power transformer. If the power supply is not fused, the transformer will go up in smoke from the heavy current overload. This is why it is never advisable to operate a TV set, black-and-white or color, with the horizontal-oscillator tube out of the circuit, or if the tube or circuit is defective.

Again, I hope this information helps. The RCA New Vista sets, which used 6CW4/6DS4 Nuvistor (aka acorn) tubes as RF amplifiers, were very good ones with excellent pictures, and seemed to be built well; I remember seeing a few such sets when I was in grade school in the 1960s. Our school had a fleet of these, operating from a master antenna system, and they all had great pictures on the PBS (then called NET for Natl. Educational TV) channel in Cleveland.

Good luck and very kind regards,

I'd just replace the fusable resistor with a fuse in series with a new resistor. According to the markings, I'd guess that it had a resistance of 7.5 ohms. Not at all critical. Anything from 5 to 10 ohms will work. As for the fuse's current rating, well, the horizontal is the current hog, and the rest of the set likely comsumes as much for everything else. Take a look at the nameplate watts rating. Add up the wattage of the tube heaters and subtract that from the nameplate. I see what looks like a power transformer, so you'll need to measure the high voltage secondary, likely 120 to 250VAC. Once you have that, divide the watts by it and that will yield a nominal current approximation. Size the fuse about twice that.

Once you install this, use a "dim bulb" tester. That's a large light bulb, 200W or so wired in series with the TV set power plug. After the tubes are warmed up, the bulb should only glow dimly. If it stays bright, you likely have a short on the B+. The bulb is to limit powerline current to hopefully avoid frying the transformer.

The fusable resistor affects the entire set, not just the high voltage. If sound exists, this resistor is not open and probably ok. I would suspect the high voltate rectifier tube though. From the picture, this set appears to be a B&W set and would not have the 6BK4 tube.

This sets chassis looks similar to two RCA New Vista B&W tvs that I have. I have them both on cable and they have excellent pictures.

The series light bulb is a good suggestion where a short circuit is suspected, but since you have sound the power supply is probably ok.

Here is how I test for HV:

First, get a neon bulb tester like you use to check for 120 volts ac at an outlet. Hold the neon bulb carefully near the output lead of the flyback with set on. Keep fingers away from the HV components. Just hold the bulb near it...no direct connection. If it lights there is AC coming out of the flyback.

2. If there is no lamp indication, hold the bulb near the insulation of the Horizontal output tube plate lead. If the bulb lights here, the primary portion of the flyback (Horiz. tube and damper) are working. If no light indication proceed to step 3.

3. REMOVE the plate cap from the horizontal output tube. Make sure that it is not connected to the tube. Connect the voltmeter to the disconnected plate lead. You should have the B+ voltage, around 280 volts. If there is no voltage, either the damper is not functioning or the flyback winding is open. In such case, check the damper plate for B+ voltage.

4. If there is plate voltage at the plate cap hook it back up and measure for negative grid voltage at the Horiz output grid. There should be around -30 to -50 volts. No negative voltage indicates the horizontal oscillator is not working. Don't run the set for long like this as the horiz output tube is drawing too much current and you can burn out the flyback winding.

Can you hear the whine of the Horiz Osc come up when you run the set?

If it uses a coil type Horiz Hold it might just be several turns off, killing the Osc.
That orange looking coil on the bottom right of the bottom P.C. board looks like it might be the horiz coil?

As a coincidence, I just started working in the last few days on a similiar set I have. Mine must be a little older as it is not "New Vista" (doesn't use a Nuvistor in the tuner) but from the pictures the chassis is very, very similiar. Mine also has HV problems. I hooked up my Sencore sweep circuit tester yesterday and near as I can tell its telling me I have a bad yoke. I have HV at the flyback by neon light test and I have horizontal whine; the tester shows cathode current on the HO as too high. Disconnecting the "fat" lead of the yoke and hooking up the Sencore got me a vertical white line-also got me a bunch of smoke, apparently one of the caps near the HO didn't like that much! I don't have the Sams, anyone know a number (RCA or aftermarket) for the yoke? I have a few in my stash.

Do you have any part numbers? I also have some yokes of this vintage.

Gonzo:
Well its been one loooong time since I've seen one of those fellers. Everyone's right on the 7.5 ohm fusible resistor . Your photos resolution was good enough to almost make out the one thing that you certainly needed for our further research¡ng, the sets chassis number, but seems like I just slightly make out its ink stamping presence on the chassis just below the HV cage.
RCA b&w TV chassis designator prefixes are KCS while their color chassis are CTC, so see if that might be KCS128, etc. The little green tag center top has the units serial number and possibly the model number and there is typically a dupe label on the back of the cabinets cover plate and the third was on the new sets cardboard packing box.
The HV cage reveals an older wax covered flyback xformer and it feeds to what should be a 1B3 (or counterpart) , the kines hi voltage rect tube. Handle that cap and lead with kid gloves if you go in there , as its probably age hardened and fragile/brittle.
Also, outside, the hoz out put tube is probably a 6DQ6, watch for brittle wire on its plate lead also at the cap plus use a small screwdriver between the bottom flange of the plate cap and the cap above or you'll typically end up with the tube plate cap pulling off the tube proper.
I scanned the chassis looking for that black paper capacitor and the closest black cap visible on the back side was the bottom left corner of the vert/hoz/sync PCB , but that black cap is a plastic housing, with the rest of the caps being quality epoxy dipped units. Then I saw another ref of yours to the fusistor and its socket, that ,<<black paper cap>> beside it is an electrolytic cap in the power supply's voltage doubler circuit with its cardboard protective insulative shield, and they were dull matte black..even on day one. Seems like they used a lower than usual raw B+ AC on the power transformer on the bottom right corner,... ( thats why all of your tubes are lit, this is no series string filament chassis)..and then voltage doubled it to get the full B+ voltage
and that cap we referred to was used in that doubling stage circuitry. Also,in that area seems like there is a disc shaped current inrush thermistor just to the right of the cap just mentioned. I am sure that its bonded 2 leads on each side have solder crazing so be very carefull when probing near it also, due to its potential fragility.
Looks like at the bottom of the chassis there was an oxidation of the right of the interlock sockets pins and increased resistivity with an increase in thermal temperature to the state of a charring of the surrounding urea bakelite that it was pressed into. The left pin almost looks as if it is missing ?
The mentioned right bottom inductor swings between three potential candidates, probably , the hoz osc coil, possibly a hoz lin coil .Seems like the hoz width reduction, was accomplished on this unit with a mylar clad brass strip that encircled the neck of the kine and was slid inward towards the front of the yoke to decrease the width.
Lastly if you are curious of the sets vintage grab one of the most likely to be an OEM tube in the AF/VIF/SIF PCB ¡¦at the top left corner of the chassis and see if it might be an, e.g. 59-16 code date (+-5 years), that is, the 16th week of 1959.

BTW I have always been impressed with the mechanics of the fabrication of the bottom center potentiometer, just down below your speaker. It utilizes a thin conical tapering of the control shaft which frictionally couples into the triad of ball bearings surrounding it. The bearings are in turn inset into a round disc that rotates the pots wiper contact. The gearing ratio is almost in the order of 10x giving somewhat of a definite vernier adjustment to that pot, as compared to a typical pots 270 deg rotational axis . This was way back in the day when ten turn pots were lab items at an arm and a leg expense, and even today, they don't give them away. Also would you confirm this to be the only thing of logic for that control to be, your hoz hold control.
Provide the chassis number and I'll see if I can be of some help on diagnostics/troubleshooting.

{ the same Gonzo..?...with...Sony SS TV....with squirrelly sound problem ...turned out that ur small 14 pin MTS sub module was the culprit....KARL}

...And now for another episode of Where Are They Now...

Y'know, I had forgotten about this thread, but just did a quick search and sure enough-- here it is..!

See, just this past Sunday, I encountered this very TV set at a hamfest. Yes, literally, this TV. ...'cause Gonzo was the one selling it. :-)

Anyway, I had passed by this set a few times on my rounds of the hamfest flea-market (mostly trying to find some excuse not to buy this thing, even at five bucks). I stopped by later on to take another look at this set, and got into a conversation with the seller, who turned out to be none other than GonzoTheGreat here at AK..! Long story short, Gonzo simply gave me the set just so it would have a new home. [Thanks again Gonzo!] Gonzo mentioned the bad HV, but I hadn't yet realized he had actually asked about it here on this forum.

After I got home and got around to popping the back off this set, I immediately noticed that the fusible resistor looked pretty fried, which an ohmeter demonstrated was indeed the case. I popped in a new one (I happened to have a few NOS ones around), and made a few quick visual and electrical checks (turns out to be a pretty clean set, really), and put the set on a variac to let it 'cook' for a while. Then I turned 'er up to 100%, crossed my fingers, and everything came up a-okay..! I kept waiting to see if the B+ supply would blow the fusistor again, but it never happened. The HV section seems strong, with no arcing or hissing, and no signs of blooming. I put on a pattern generator, and saw that the picture geometry was excellent! Other than a few minor things, the only real issue I noticed was weak IF (turned out the first IF tube was gassy; a replacement took care of that problem). neat to see something broken become usable once again..?]

Anyway, I was going to PM Gonzo just to let him know (though now he probably wishes he had kept the TV..!), but then I started thinking-- didn't Gonzo actually post about this set a few months ago..? :-)

By the way, to answer a few of the questions that were asked about this set, it's a KCS-130. The latest date codes on the apparent "virgin" tubes in this set (at least those that have date codes) are 61-52, which suggests this set was made in early 1962. This set still has a 17" picture tube, though; hadn't those pretty much been replaced by the (more square-cornered) 19" tubes by about that time..?

Edd-- I too had noticed (and wondered about) the oddly-designed multi-turn pot, and you're right-- it's the horizontal hold control. Thanks for the info on its design!

Assuming I did it right, attached is a pair of images showing the set in action.

Attaboy! You da man! Glad to see that you nailed the problems so fast. I'll keep you in mind if I come across any more sets. Too bad I couldn't save that Muntz for you...

As for wishing I'd kept the set, nope. Not at all. I have little or no interest in old TVs. So I gave away the set to a good home (can I pick 'em or what?) so it wouldn't get banged up bouncing around the car going from hamfest to hamfest. I had also considered hauling it off to St Vinnies but they would probably toss it since it wasn't 100% working. So now that it's working I can sleep easily. Yeah I worry about my stuff going to good homes.

If you want to thank me, toss AK the five bucks I was going to charge.